Carbon monoxide, free-radical

Because di-/ fZ-alkyl peroxides are less susceptible to radical-induced decompositions, they are safer and more efficient radical generators than primary or secondary dialkyl peroxides. They are the preferred dialkyl peroxides for generating free radicals for commercial appHcations. Without reactive substrates present, di-/ fZ-alkyl peroxides decompose to generate alcohols, ketones, hydrocarbons, and minor amounts of ethers, epoxides, and carbon monoxide. Photolysis of di-/ fZ-butyl peroxide generates / fZ-butoxy radicals at low temperatures (75), whereas thermolysis at high temperatures generates methyl radicals by P-scission (44). 

Examples of perfluoroalkyl iodide addition to the triple bond include free radical addition of perfluoropropyl iodide to 1 -heptyne [28] (equation 21), thermal and free radical-initiated addition of lodoperfluoroalkanesulfonyl fluorides to acetylene [29] (equation 22), thermal addition of perfluoropropyl iodide to hexa-fluoro 2 butyne [30] (equation 23), and palladium-catalyzed addition of per-fluorobutyl iodide to phenylacetylene [31] (equation 24) The E isomers predominate in these reactions Photochemical addition of tnfluoromethyl iodide to vinylacetylene gives predominantly the 1 4 adduct by addition to the double bond [32] Platinum catalyzed addition of perfluorooctyl iodide to l-hexyne in the presence of potassium carbonate, carbon monoxide, and ethanol gives ethyl () per fluorooctyl-a-butylpropenoate [JJ] (equation 25)... 

The oxides are gaseous and do not undergo reactions in the atmosphere that produce aerosol particles. Carbon monoxide is a relatively inert material with its main sinks in the atmosphere via reactions with free radicals, e.g.,... 

When dicobalt octacarbonyl, [Co(CO)4]2, is the catalyst, the species that actually adds to the double bond is tricarbonylhydrocobalt, HCo(CO)3. Carbonylation, RCo(CO)3- -CO—>RCo(CO)4, takes place, followed by a rearrangement and a reduction of the C—Co bond, similar to steps 4 and 5 of the nickel carbonyl mechanism shown in 15-30. The reducing agent in the reduction step is tetra-carbonylhydrocobalt HCo(CO)4, ° or, under some conditions, H2. When HCo(CO)4 was the agent used to hydroformylate styrene, the observation of CIDNP indicated that the mechanism is different, and involves free radicals. Alcohols can be obtained by allowing the reduction to continue after all the carbon monoxide is... 

Free-radical copolymers of vinyl chloride with carbon monoxide have been suggested to contain pendent C0C1 groups (as in. )... 

Sometimes acylium ions lose carbon monoxide to generate an ordinary carbonium ion. It will be recalled that free acyl radicals exhibit similar behavior at high temperatures. Whether or not the loss of carbon monoxide takes place seems to depend on the stability of the resulting carbonium ion and on the speed with which the acylium ion is removed by competing reactions. Thus no decarbonylation is observed in Friedel-Crafts reactions of benzoyl chloride, the phenyl cation being rather unstable. But attempts to make pivaloyl benzene by the Friedel-Crafts reaction produce tert-butyl benzene instead. With compound XLIV cyclization competes with decarbonylation, but this competition is not successful in the case of compound XLV in which the ring is deactivated.263... 

The well-known step function of 7-probes as they are commonly mounted in combustion engines of motor vehicles is much smaller with this probe and is shifted to higher air ratios. The assumed reason are reactions with intermediate combustion products, free radicals and carbon monoxide on the sensor surface whose intensity increases with lowering air ratios down to stoichiometric level. A solution for the set up based on this sensor is presented further below. 

This industrial process remains essentially unchanged from the 1950s [25], Here, a free-radical initiator is added to the ethylene monomer at supercritical conditions (276 MPa and 200-300 °C). The polyethylene remains in the supercritical solution until the pressure is lowered to around 5 MPa, whereupon it precipitates. A range of other monomers can be copolymerized, including carbon monoxide to give polyketones, as shown in Scheme 10.19 [26],... 

What is the initial source of the free radicals that are so important for oxidant development Calvert and McC igg attempted to answer this question by evaluating the many proposed reactions with their detailed chemical model. Although the actual importance of any particular source will depend on the concentration of pollutants assumed and the time of irradiation they found for a typical mixture (nitric oxide nitrogen dioxide rra/is-2-butene, formaldehyde acetaldehyde carbon monoxide water and methane) that the following reactions were the most important radical sources ... 

Photolytic. Photolysis of acetone in air yields carbon monoxide and free radicals, but in isopropanol, pinacol is formed (Calvert and Pitts, 1966). Photolysis of acetone vapor with nitrogen dioxide via a mercury lamp gave peroxyacetyl nitrate as the major product with smaller quantities of methyl nitrate (Warneck and Zerbach, 1992). 

Photolytic. Photolysis products include carbon monoxide, ethylene, free radicals, and a polymer (Calvert and Pitts, 1966). Anticipated products from the reaction of acrolein with ozone or OH radicals in the atmosphere are glyoxal, formaldehyde, formic acid, and carbon dioxide (Cupitt,... 

Smoking tobacco causes damage to endothelial cells due to free radicals present in tobacco smoke. It is estimated that each puff of a cigarette produces lO " free radicals. In addition, the resultant lack of oxygen causes damage or death to neurones, and nicotine and carbon monoxide, both present in tobacco smoke, cause an increase in blood pressure. 

In Sch. 1, if the 002 radical anion reacts with CO2 in solution, CO is formed via a dimeric intermediate in which a C—O bond is formed. A second electron transfer to this intermediate from either the electrode or 002 leads to the formation of carhon monoxide. The ultimate result of this pathway is the formation of the two-electron reduction product, carbon monoxide, and carbonate. In this reaction, a second CO2 molecule acts as the acceptor of the oxide ion formed in the two-electron reduction of CO2 to CO. Many of the features of these reactions are common to the catalyzed reactions discussed in the following. Because free C02 is not present in the catalyzed two-electron reductions of CO2 to CO, the reduction potentials can be considerably less negative than that required to form CO2-. 

The acyl radical formed from acrolein, maintaining its coordination with a catalyst, may react preferably with oxygen, rather than decompose to produce carbon monoxide, though it is generally believed that a free acyl radical is formed after the abstraction of aldehyde hydrogen by a metal. In such a case, the catalyst metal is considered as behaving as a mononuclear, not a binuclear complex. The molecular weight of the catalyst recovered from the oxidation solution was measured (Table V). 

The reaction of triplet carbenes with a persistent nitroxide such as 2,2,6,6-tetra-methylpiperidine A -oxide (TEMPO, 84) to form benzophenone would be spin allowed and >100-kcal/mol exothermic (Scheme 9.26). The reaction has a few parallels in free radical chemistry, such as the reaction of tert-butoxyl with carbon monoxide (to yield CO2) or with phosphorus (111) substrates to yield P(V) products. " ... 

The fate of the free acyl radical 68 and radical 74 is not known. Most probably it is a constituent of polymer deposits on the wall of the irradiation vessel which hitherto have not been identified more definitely.29 Moreover, the identification of methane and carbon monoxide among the gaseous products of the photolysis of 4-methylphenyl acetate (55) provides evidence for the existence of the acetyl fragment. This intermediate is expected to decarbonylate to give carbon monoxide and a methyl radical, which in turn abstracts hydrogen from the solvent.34... 

The HCo(CO)4 complex is therefore inferred to be involved in initial hydrogen transfer to carbon monoxide. This step was initially proposed to comprise rate-determining hydrogen atom transfer from HCo(CO)4 to free CO, affording a formyl radical, HtO subsequent reaction with further HCo(CO)4 would lead to the observed products (35). However, kinetic observations (the zero-order dependence on CO partial pressure) were later made which are inconsistent with such a process (36). 

Step 5 provides a higher aldehyde as a source of hydrogen in the formation of hydrogen peroxide and a potential source for the carbon monoxide which appears as an accompanying combustion intermediate. The free butyl radical continues the decadent oxidation reaction chain. 

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